Information recording media include semiconductor memory, magnetic disks, optical disks, magnetooptical disks and the like. Data stored in an information recording region of such information recording media is conventionally managed by a file system. According to a file system, an information recording region is divided into sectors, which are the minimum access units, and clusters, which are an aggregate of sectors, so as to be managed in such a manner that one or more clusters are managed as files.
A FAT file system is cited as an example of a file system which is conventionally utilized. The detail thereof is disclosed in ISO/IEC9293, “Information Technology-Volume and file structure of disk cartridges for information”, 1994.
The FAT file system is a file system which is generally used in an information apparatus such as a personal computer, where physical storage positions of data that forms a file are managed in a unified manner by a table which is referred to as FAT (File Allocation Table). Information recording media of which the data is managed by the FAT file system can share files between apparatuses that can interpret the same file system. As a result of this, it becomes possible to transmit and receive data between a plurality of apparatuses by using the FAT file system.
Such a file system is usually constructed for the purpose of managing one information recording medium. When a plurality of information recording media exist in an information processing device, the individual information recording media are managed by file systems which are independent of each other. There is a conventional management method by means of a drive and a conventional management method by means of a mount point as methods according to which an information processing device handles a plurality of information recording media.
According to the management method by the drive, the device allocates drive IDs (such as C drive and D drive) particular to the respective information recording media so as to switch the information recording medium to be accessed by using these drive IDs. In addition, according to the management method by the mount point, a tree structure of each information recording medium is allocated to a specific portion within a tree structure that is formed of files and directories managed by a main file system. Then, an access position within the tree structure is switched, so that the information recording medium to be accessed is switched.
However, it is necessary for the user to utilize a plurality of information recording media which are switched according to these methods; therefore, the user's task becomes greater as the number of information recording media increases. In addition, when a plurality of information recording media can be freely attached to or detached from an information processing device, they are allocated to a drive or an access position that is different from the one to which they were allocated at the time when they were previously attached, if the order or the positions of the media attached to the information processing device are different. In this case, it becomes difficult for the user to correctly specify an information recording medium.
As a method for solving such a problem, a method for using a unified file system where a plurality of information recording media are unified so as to integrate the interfaces with applications into one has conventionally been proposed. This method is disclosed, for example, in JP-A 2000-163298. According to this conventional method, a plurality of information recording media are managed by individual file systems. Thus, the unified file system for unifying the respective file systems is provided in a layer above these, so as to integrate the interfaces with applications into one. In this manner, the file systems are divided into two layers so that they are manageable; thus, the interfaces with applications are unified, reducing the task of the user.
However, the above-described conventional art has the following problem. An object of the conventional file management method is to facilitate an increase in recording capacity in an information processing device by adding an information recording medium where an arbitrary file system has been constructed to the information processing device. Therefore, it is not assumed that a plurality of information recording media are utilized in a such manner that they are freely attached to or detached from a plurality of information processing devices. In addition, a case is not assumed where files having the same name exist within a plurality of information recording media. When files having the same name exist, an application cannot determine which file has been accessed, due to the unified interface. In the worst case scenario, therefore, all the files having the same name will become inaccessible.
The present invention has been made in view of the above-described problem, and an object thereof is to make an application think that the entirety of a plurality of information recording media is virtually managed by a single file system when individual file systems are constructed for the plurality of information recording media, and to implement a method for an application to access the respective files, even when files having the same name exist.